Birth defects have long captivated the human imagination. As Samuel Taylor Coleridge wrote, “The history of man for the nine months preceding his birth would be far more interesting and have events of far greater moment than all three-score and ten years that follow.” Over the last 40 years, fetal diagnosis through imaging and fetal sampling has improved tremendously, allowing for earlier and more accurate diagnosis of birth defects. Surgeons are increasingly called upon for management of these anomalies before birth. In this chapter, we present general principles of fetal surgery, methods of fetal access, diseases that are amenable to fetal intervention, and a brief discussion of the future of fetal surgery.